Means for suppressing harmonics



Oct. 16, 1928. 1,687,585

J. A. O NEIL MEANS FOR SUPPRESSING HARMQNICS Filed May 16, 1924 SOURCE kiiiiia James QNeih.

H is Attqfh e'y.

Patented Oct. 16, 1928.

UNITED STATES PATENT OFFICE.

JAMES A. ONEIL, F LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

MEANS FOR SUPPRESSING HABMONICS. 4

Application filed May 16,

My invention'relates to the suppression of harmonics which are likely. to interfere with 'the transmission of sound, and has for its object the provision of an improved means 5 for suppressing or eliminating the harmonics occasioned by interruption of the current supplied from a power line through a transformer or. similar inductive device.

It is well known that harmonics are pro- 0 duced by a transformer which is supplied with current while its secondary circuit is open and that theeifect of the disturbances caused by these harmonics is not confined to the power circuit to which the transformer is ;connected, but may affect telephone lines inductively 'related to the power circuit. It has also been found that the inductive disturbances produced by such harmonics may seriously interfere with radio transmission andreception' of sound. In accordance with. my invention, these diificulties are avoided by the provision of. animproved arrangement for short-circuiting the transformer coil upon-the interruption of its secondary circuit.

My invention will be better understood on reference to the following description when considered in connection with theaccompanying drawing and its scope will be pointed out in the appended claims.

, Referring to the drawing, the single figure thereof shows my invention as utilized in connection with load deviceswhich areillustrated as lighting fixtures comprising lamps 1 hav-. ing their supply transformers connected in a v series circuit which may be of the constant current type. Current is supplied to each of the lamps 1 from a transformer winding through the operating coil 3 of a mercury switch whichis provided for short-circuiting the secondary coil of the transformer coil when the circuit of the lamp 1 is interrupted. Each of the mercury switches comprises a container 4 which is bifurcated at its lower end to contain separable mercury bodies 5 and 6 and which contains a magnetic member 7 movable in response to energization of the operation coil 3. A negative temperature coefficient resistance rod 8 of silicon or like material is connected in series with the mercury switch to the transformer coil 2. Either auto transformers 2 or double core transformer 9 may be provided to regulate the amount of current supplied to the lamps 1.

1924. Serial No. 713,867.

When the secondary circuit of the transformer 1s closed through the lamp 1, the coil 3 is energized, the member 7 is maintained in harmonics which would be produced by supplying current to the coil2 with its secondary circult open.

When the load circit is deenergized, the member 7 of each lamp will move to its down position,'thereby connecting the rod 8 across the coil-2. If the circuit is now energized, the winding 2 and rod 8 are connected in parallel and the proportion of current carried by each will be dependent upon the relation between the values of their impedances. In order for the switch to open under these conditions, it is necessary that the voltage drop across the rod 8 be high enough to insure that sufficient current to operate the switch is supplied to the switch operating coil 3. The initial resistance of the rod 8 should therefore be comparatively high. A rod with a permanently high resistance, however, would be objectionable for the reason that much energy would be wasted in heating it when the lamp failed to operate. The resistance of therod 8 should therefore be high when the circuit is energized but should decrease if the lamp 1 fails to operate. In accordance with my invention, these conflicting requirements are met by providing a rod or member having a resistance which decreases as its temperature is raised. In this manner, excessive losses due to heating of the rod are avoided and sufficient current is provided to operate the switch at starting.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination of a series load circuit, a load device, a transformer comprising a primary circuit connected in series in said load circuit and a secondary circuit arranged to include said load device, and means for.

cuit said primary circuit through said element in response to the failure of the circuit of said load device.

2. In combination, a constant current se ries circuit, current transformers connected in series relation with said circuit, load devices associated with said trai'isformers and arranged to be supplied with current throu h their respectively associated trans't'orunr, and means for preventing the saturation of a transformer in case of the failure of the circuit of the associated'load device whereby to avoid the production of harmonic currents in the transformer including a resistance element having a negative temperature coetii cient and a switch operative in response to the failure of the circuit of the load device to connect said resistance element across a winding of the transformer.

3. In combination, a constant currentseries circuit, current transformers having their primary windings connected in series in said circuit, load devices associated with said transformer and arranged to be supplied with current through their respectively associated transformers, and means for preventing the saturation of a transforn'ier in case of the failure of the circuit of the load device whereby to. avoid the production of harmonic currents in the tltlIlSfOIl'llGl' including a resistance element having a negative temperature coefficient and switching means operative when the circuit of the load device is intact to open-circuit said resistance element and when the circuit of the load the vice fails to connect the resistance element a tross a winding of the transformer.

In witness whereof, I have hereunto set myhand this 13th day of May, 1924.

JAMES A. ONEIL. 

